Marine electrocleaning and electropickling apparatus



July 19, 1949. I

. a (30X 2,476,286 MARINE ELECTROCLEANING AND ELECTROPICKLING APPARATUSFiled Aug. 25, 1944 GEORGE C. Cox

ww w Patented July 19, 1949 UNITED OFFICE 'MARINE ELECTRUCLEANING ANDELECTRO- PICKLENG APPARATUS (Granted under the act of March 3, 1883, asamended April 30, 1928; 376 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment of anyroyalty thereon.

This invention relates to improved types of apparatus forelectrolytically cleaning or electrolytically pickling the metal hull ofa ship or other metallic structure which is submerged in sea or sea portwater.

One of the chief factors militating against the commercial use of suchelectrolytic methods for cleaning or pickling the hull of a ship is thedanger that some piece of metal projecting from the hull may cause ashort between the hull and the adjacent electrode. With the appreciableamount of power available, such a short would draw a heavy are whichcould quickly cause considerable damage to the hull.

The primary object of this apparatus is to provide a simple economicaland effective means of preventing a direct short between the mainelectrode members and the adjacent hull surface and of limiting any arebetween the screening electrodes and adjacent hull surface to a valuewhich is incapable of damaging the hull. These screening electrodes orbars should usually be of much higher conductivity than the electrolyte.

In Figures 1 to 4 inclusive, which represent schematic diagrams of theessential parts of the apparatus, similar numbers refer to similarparts.

Figure 1 is a schematic cross sectional View of one form of theapparatus, taken along the line i--! of Figure 3.

Figure 2 is a cross sectional view of Figure 1 along the lines 2-2 ofFigure 1, showing the arrangement of a float tank.

Figure 3 is a cross sectional View of Figure 1 along the line 33 ofFigure 1, showing the arrangement of the electrode supports and connections.

Figure 4 is a cross sectional view along the line -4 of Figure 3,showing in greater detail the means of effectively distributing thecurrent over the surface to be cleaned. This view indicates the lines ofcurrent flow from the electrodes H to high conductivity screening barsl4 and to the metal surface l5 Undergoing treatment.

Electrodes i0 and II are fastened to current distributing heads l2 andI3 respectively. The

bars M are arranged between the electrodes iii and ii and the metalsurface IE to be cleaned. In the various figures the surface l5 to becleaned is represented as being the bottom of a ship hull it. Theseveral parts Ill, ll, l2, I3 and M are securely held by the framemembers I1 and it which are substantially non-conducting. For simplicityin illustrating the essential parts, the frame members are shown ashaving considerable thickness; in actual construction these parts wouldbe made as thin as is consistent with good engineering practice.

Current shields I9, 26, 2i and 22 are also secure- 1y held by the framemembers I! and I8. These current shields are substantiallynon-conducting and extend the full length of the electrodes. Theseshields should be setat such an angle from the vertical that any foulingmatter, rust or other sludge which falls between the electrodes willslide down the sides of the shields and out the bottom through theopenings 23 and 24. The efficiency of the device is a function of theability to concentrate high current densities upon the surface areaundergoing treatment at any specific time. If non-conducting shieldscould be continuous around the side of the electrodes away from the workand could extend up against the work the leakage current loss would bezero and the current efiiciency of the device would be a maximum.Obviously such a situation is impractical and the long narrow openings23 and 2d are therefore provided for the discharge of waste matter. Ifthese openings are made only sufflciently wide to discharge waste matterthe leakage currents will not be excessively large as has beendetermined by various tests in regard to practical and useful shieldingmethods. Furthermore, these openings 23 and 24 serve another essentialpurpose which is that of supplying an ample circulation of fresh seawater to the device without which the voltage efficiency soon drops offdue to the depletion of conducting ions in the paths of high currentdensity.

As illustrated in Figures 1 and 2 this specific apparatus for cleaningship bottoms has cylindrical float chambers25 and 26 built into each endof the apparatus.v For small cleaning equipments these chambers can bemade of the pro-per size to keep the equipment barely floating. Ho"ever, for the convenience of handling large equipments the floatchambers should be made like diving bells with hose connections 21 and28 for admitting or removing compressed air and with water vent holes 29and 30 for forcing out or letting in a proper amount of water ballast togive the desired upward pressure on the bottom of the ship. Because thesame apparatus must be able to clean the vertical sides of the ship, thehose connections and the water vent holes are usually located at 45degrees from the vertical or horizontal as shown.

As illustrated, the entire equipment is held firmly together by steelbands 3| and 32 at each end of the frame assembly. These bands act assled runners and should extend continuously around the frame assembly insuch a fashion that the equipment will slide on the bottom of the shipeven if it should be accidentally turned upside down. To these bands 3|and 32 cable eyes 33 and 34 are generally attached. To these cable eyesare attached cable bridles 35 and SE for pulling the equipment in eitherdirection across the bottom of the ship as desired.

As illustrated in Figure 3 the electrodes I l and distributing head I3are made of metal, either iron or steel; although with slightmodifications graphite or other non-metallic electrode material may beused. Into the distributing head i3 is screwed a current conducting bolt3! under which the cable terminal lug 38 is fastened. Into the cable lug38 is brazed or soldered the flexible insulated power cable 39 whichleads to the desired high amperage power source, the other terminal ofwhich is generally connected to the ship. To prevent corrosion of thecurrent carry ing bolt 31 and terminal lug 38, the terminai box 48 isgenerally filled with some standard sealing compound like "potheadcompound. Another current carrying cable not shown is connected to thecurrent distributing head [2 in a similar manner as above described.

One or more current distributing heads may be used in such an apparatusdepending upon whether cleaning or pickling is desired and upon whetherdirect current is to be equally divided between each distributing head.If alternating currents or pulsating direct currents are used with thisapparatus, the number of separately controlled or operated heads willdepend upon the specific results which are desired. It is thus seen thatthe apparatus and method of operation thereof is quite flexible and canbe connected for various specific cleaning or pickling uses withoutdeparting from the principles herein set forth.

Having described the apparatus more or less in detail as well as thevarious secondary objects thereof, the primary object of this apparatuswill now be discussed. As previously mentioned the primary object ofthis equipment is to effect a high concentration of current on a givenarea oi. hull surface with a minimum expenditure of power and at thesame time to prevent the accidental formation of an arc to the hull of aship which would damage the ship. The desired protection is aiiorded andefliciency increased by interposing a set of bars I of high electricalconductivity between the electrodes H1 and H and the surface I5 which isto be cleaned. The cross section of these bars l4 and the electrodes ii)and l I is round, square or rectangular as required to meet the specificdesired design.

The overall efi'iciency depends not only upon the current efficiencywhich has been discussed but also upon the voltage efliciency which willnow be discussed. Obviously the voltage efficiency will be a maximumwhen a minimum voltage drop occurs between the hull l5 and theelectrodes It or H. Referring to Figure 4. if the resistance can bereduced between the electrodes 2'! and surface l5 undergoing treatmentthe voltage drop will be reduced almost in a direct roportion thereto.Thereiore by placing bars I l of high conductivity in comparison to seawater in the paths of current flow between the electrodes H and thesurface 15 undergoing treatment, the overall resistance is materiallyreduced and similarly the voltage efiiciency is raised. In other Wordsthe efiective gap between the hull of the ship and the electrodes 10 orH can be made a minimum by interposing such conducting bars 14 betweenthis surface and its coacting electrodes. Furthermore, these bars [4have the important function of preventing a direct short circuit of thepower source which could occur if these bars were not used. For example,in normal operation with approximately equal conductance in the twowater gaps, a short from the ship hull to the bar I4 would not evendouble the current flow from the one coacting electrode and no damagecould be done. This type of safety gap becomes very important wherelarge powered multiple electrode cleaning or pickling units are in use.

Another function of such an arrangement emhodying an electrode and acoacting bar Id of high electrical conductivity in an electrolytic pathof high current flow is that the current is distributed more uniformlyover the surface undergoing treatment. This condition is illustrated inFigure 4.

For convenience in clearly illustrating the principles and essentialparts involved, the electrodes iii and H and the high conductivity barsM are shown with their axes at right angles to the direction of movementof the apparatus illuatrated by the two arrows near the cable ofFigure 1. However, it is often desirable particularly with largeequipments to have the axes of these electrodes l0 and H and the highconductivity bars M parallel to the direction of motion of theapparatus.

This equipment can be described as comprising one or more electrodes H]or H of opposite polarity to the metal surface 15 undergoing treatmentand adjacent thereto, and one or more bars M of materially higherconductivity than the electrolyte which are interposed in the paths ofoptimum current flow between the metal sur face it? and the one or moreelectrodes it or H. An apparatus incorporating the above features mayalso include a high resistance shield almost completely surrounding theelectrodes on the side of the electrodes opposite to the surface undengoing treatment if desired. An apparatus incorporating all of the abovefeatures may also one or more floats firmly attached to the above parts,the bouyancy of which may be controlled at will.

The invention may be regarded in broad terms as essentially an apparatuscomprising a main electrode of opposite polarity to that of the shipshull, mounting means for said electrode positioning it adjacent thehull, a secondary electrode mounted on said mounting means andpositioned between the main electrode and the hull, spacing meansseparating the main and secondary electrodes so as to insure that theeffective distance between them is sufficient to allow the sea waterelectrolyte to act as a current limiting resistance and control orprevent arcing or other destructive current flow. It is desirable thatthe secondary electrode have a low effective resistance.

It should be noted that the grouping of the essential parts as hereinshown is illustrative of one useful embodiment of this invention andthat the physical rearrangement of these parts may be made as foundnecessary for each specific application thereof, and in accordance withthe appended claims.

Having now described my invention, 1 claim:

1. Apparatus for electrolytically cleaning the surface of metal partswhich are submerged in an electrolyte, comprising a frame, a pluralityof elongated electrodes mounted in said frame, a plurality of elongatedhighly conductive ele ments mounted in said frame between saidelectrodes and the surface to be cleaned and electrically insulated fromand spaced from said elec trodes, said highly conductive elements beingin aplane parallel to said electrodes, electric cur rent shieldspartially surrounding said electrodes and highly conductive members,said shields being situated to collect material removed from the surfacebeing cleaned to direct such material away from the electrodes andhighly conductive elements, and means to cause an electric current toflow between said electrodes and the surface to be cleaned.

2. Apparatus for electrolytically cleaning the surface of metal partswhich are submerged in an electrolyte, comprising a frame, a pluralityof elongated electrodes mounted in said frame, a plurality of elongatedelements of higher conductivity than said electrolyte and mounted insaid frame between said electrodes and the surface to be cleaned, saidconductive elements bein insulated from direct electrical contact withsaid electrodes, electric current shields partially surrounding saidelectrodes and conductive memhere, said shields also mounted upon saidframe and arranged to collect material removed from the surface beingcleaned so that the collected material is directed away from saidelectrodes and conductive elements, means to cause an electric currentto flow between said electrodes and the surface to be cleaned throughsaid conductive elements, and means for moving said frame along thesurface to be cleaned.

3. Apparatus for electrolytically cleaning the surface of metal partswhich are submerged in an electrolyte, comprising a frame, a pluralityof elongated electrodes mounted in said frame, a plurality of elongatedelements of higher conductivity than said electrolyte and mounted insaid frame between said electrodes and the surface to be cleaned, saidconductive elements being mounted parallel to said electrodes andinsulated from direct electrical contact with said electrodes, electriccurrent shields partially surrounding said electrodes and conductive memhere, said shields also mounted upon said frame and arranged to collectmaterial removed from the surface being cleaned so that the collectedmaterial is directed away from said electrodes and conductive elements,means to cause an electric current to flow between said electrodes andthe surface to be cleaned through said ccnductive elements, and meansfor moving said frame along the surface to be cleaned, said frameincluding buoyant means.

4. Apparatus for electrolytically cleaning the surface of metal partswhich are submerged in an electrolyte comprising a frame, a plurality ofelongated electrodes mounted in said frame, a plurality of elongatedhighly conductive ele-' ments mounted in said frame between saidelectrodes and the surface to be cleaned and elec" trically insulatedfrom and spaced from said electrodes, electric current shields partiallysurround-- me said electrodes and highly conductive members, saidshields being situated to collect material removed from the surfacebeing cleaned to direct such material away from the electrodes andhighly conductive elements, and means to cause an electric current toflow between said electrodes and the surface to be cleaned.

GEORGE CHANDLER 06X.

REFERENCES SITE!) The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 498,707 Crane May 30, 1393820,105 Frazier May 8, 1906 981,922 Frazier Jan. 17, 1911. 1,154,092Burdett Sept. 21, 191.5 1,794,973 McBride Mar. 1931 1,850,426 TyrrellMar. 22, 1932 2,200,469 Cox May 14, 1940 2,232,019 Beckwith Feb. 18,1941 2,319,624 Olsen MaylS, 1943 FOREIGN PATENTS Number Country Date26,504 Great Britain 1912 OTHER REFERENCES Electroplating with ChromiumCopper and Nickel, Freeman and Hoppe, 1930, p. 128.

Metal Industry, April 28, 1944, The Distribu tion of Electrodeposits, p.267.

